Mount Laguna Observatory (MLO) is an astronomical observatory owned and operated by San Diego State University (SDSU). The telescope was operated in partnership with the University of Illinois at Urbana-Champaign (UIUC) until 2000. MLO is located approximately 75 kilometers east of downtown San Diego, California (USA) on the eastern edge of the Cleveland National Forest in the Laguna Mountains and near the hamlet of Mount Laguna.